The following studies will be conducted during the year 09-01-78 to 08-31-79: 1. The relationship between metabolic, histological and external signs of deficiency in rapid, synchronously induced vitamin A deficiency. Our studies of the signs, sequence of appearance and interrelationships in synchronously induced vitamin A deficiency will be continued to gain a better understanding of cause-effect relationships in deficiency. 2. Metabolite patterns in vitamin A deficiency. Changes in tissue, plasma and urinary amino acid and metabolite patterns will be determined as a function of time after onset of deficiency. 3. Calcium excretion patterns. The kinetics of urinary calcium excretion in relation to other early signs of deficiency will be determined. 4. Vitamin A status and drug metabolism. The molecular basis of decreased cytochrome P450-mediated hydroxylations following the onset of synchronous vitamin A deficiency will be investigated. 5. Receptor proteins. The binding of intravenously injected labeled vitamin A to intra-cellular membranes of liver and seminifuous tubules will be characterized. 6. Immune responses in vitamin A deficiency. Changes in lymphoid tissue morphology, cell mediated immunity and the quantity and quality (Ko) of systemic and secretory antibodies will be studied.